JPH06331490A - Leakage detector and leakage position detection - Google Patents

Abstract

PURPOSE:To prevent erroneous signals from being generated frequently in a leakage detector which is constituted of an optical fiber and a swelling material. CONSTITUTION:A swelling material storage chamber 110 is constituted so that it prevents a swelling material 109 before swellinq from moving and constrains the swelling material 109 so that the swelling material 109 swells toward an inner space 108. Also, a leakage substance introduction part is provided at the wall part of a housing 111 opposing an inner space with the swelling material 109 in-between. A light reflecting part 113a is provided on both surfaces of a screening member 113 mounted on the swelling material 109. Before the swelling material 109 swells, a screening member 113 is positioned outside an optical path and light passes between a pair of optical fibers 101 and 101'. When leakage is detected and the swelling material 109 swells, the screening member 113 screens the optical path and reflects incident light toward the optical fiber at the incidence side. Occurrence of leakage is detected according to the presence or absence of the reflected light. The inner space 108 and the pressure control chamber 115 which are constituted to be in airtight are made to communicate with each other through a communication path 116.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a swelling material that swells when absorbing a specific substance and an optical fiber to detect a leaked substance that has become liquid or vapor, and a leak detector that uses this leak detector. The present invention relates to a method for detecting a leak detection position.

[0002]

2. Description of the Related Art Chemical equipment for manufacturing petroleum products, petrochemical products, chemical products, etc., iron-making equipment, boilers for burning various fuels including nuclear fuel, power generation equipment, semiconductor manufacturing equipment, etc. 2. Description of the Related Art There are known leak detectors that detect various leaked substances such as various liquids leaked from oil such as oil, organic solvents, harmful substances, aqueous solutions (including radioactive aqueous solutions, acids, alkalis and pure water) and vapors thereof. As a place where the leak detector is used, there is a high possibility that a leak will occur from the equipment or the machines that make up the equipment, such as the gland and mechanical seal of rotating machinery, the gland of valves, the joints and welds of pipes, equipment. There are welds and manholes. Further, the places where the oil leak should be detected by the leak detector are the pits of tanks and yards, the pits of pumps and yards.

Hitherto, the detection of leakage of various leaked substances from various facilities has been carried out by a human being who travels around the facility machine and discovers it with his five senses to prevent accidents and disasters and manage the facility. In addition, recently, in order to save the labor, a pair of electrodes are placed with a substance whose electrical resistance changes in contact with these leaking substances, and a current is passed between the electrodes to cause electrical resistance. Leakage detectors that measure changes and detect leaks have been put into practical use. However, such a leak detector is large and expensive, and has a problem that an explosion-proof structure is required in a place where flammable materials are handled, so that its spread is hindered.

Therefore, various leak detectors for detecting leaks by using light instead of electricity have been proposed. For example, JP-A-56-110036 discloses a leak detector in which the ends of two optical fibers whose optical axes are aligned with each other are supported by a water-swelling material and a core of one or two optical fibers. A leak detector is disclosed in which an end portion is arranged toward a reflecting plate supported by a water-swelling material. These leak detectors detect changes in coupling efficiency and changes in the amount of reflected light to detect water immersion in optical fiber cables and the like. Further, Japanese Patent Laid-Open No. 2-147835 also discloses a leak detector that utilizes the swelling of a water-swelling material to cause an optical axis shift between two optical fibers to detect a leak.

[0005]

However, in the conventionally proposed leakage detector using the optical fiber, the influence of the vibration applied from the outside, the difference in the swelling mode of the swelling material due to the difference in the introduction mode of the leakage substance, No measures have been taken against the effects of changes in ambient temperature and the effects of substances not absorbed by the swelling material (particularly liquids). Therefore, the following problems have occurred.

(1) The vibration applied from the outside causes the optical fiber and the swelling material to vibrate, causing malfunction.

(2) When the introduction mode of the leaked substance is inappropriate, the swelling material locally expands, or the swelling direction is not fixed, and a malfunction occurs.

(3) Malfunction occurs due to expansion of the internal gas due to temperature rise.

(4) When the leaked substance is mixed in the solution, the solution enters the detection space in which the end of the optical fiber is housed and adheres to the end face of the optical fiber or the reflecting surface. Malfunction occurs. If the leaked substance is contained in the vapor, the vapor enters the detection space and an erroneous signal is generated.

Further, in the conventional leak detector, when leak detectors are arranged at a plurality of points to detect leaks at the respective points,
Although it was possible to easily detect the occurrence of leakage, it was not possible to easily specify the position and the range of occurrence of leakage.

It is an object of the present invention to provide a leak detector which uses an optical fiber and a swelling material, and which produces few false signals.

Another object of the present invention is to provide a leak detector which can detect leaks of various kinds of oils, organic solvents, harmful substances, aqueous solutions and vapors thereof without requiring an explosion-proof structure. To provide.

Still another object of the present invention is to provide a method for easily detecting a leak position when using a plurality of leak detectors.

[0014]

SUMMARY OF THE INVENTION A leak detector to which the present invention is directed is such that an end portion is held by a holding portion provided inside the housing such that the optical axes of the housing and the housing are aligned with each other, and the inside of the housing is held. A pair of optical fibers for transmitting and receiving light through the space, a leaking substance introducing portion provided in the wall of the housing, and a swelling material accommodating chamber provided in the housing, which is a detection target entered from the leaking substance introducing portion. A swelling material that absorbs and swells the leaked substance, and moves in the internal space by utilizing the swelling of the swelling material, and when the swelling material swells, locates the light reflection part in the optical path between the pair of optical fibers. And a shielding member that reflects the light incident on the internal space toward the optical fiber on the incident side.

As the pair of optical fibers, a multimode optical fiber or a bundle optical fiber can be mainly used.
The structure of the holding portion of the pair of optical fibers is arbitrary, but for example, a rigid support base made of engineering plastic such as epoxy resin or metal such as stainless steel or aluminum by a method such as molding or mechanical molding is provided, The end surface of the optical fiber may be aligned with the side surface of this rigid support and fixed so as to form a smooth surface. Alternatively, the exposed cladding and core except for the coating on one end of the optical fiber may be inserted into a tubular ferrule and fixed, and this may be bonded and fixed to a rigid support. The end portion of the optical fiber may be held by the holding portion with the coating.

As the swelling material that swells in contact with various leaking substances, leaking substances to be detected are gasoline, naphtha, kerosene, heavy oil, crude oil, electrical insulating oil, machine oil, lubricating oil, soybean oil, cottonseed oil, olive oil, Highly oil-absorbent resin for various hydrophobic organic liquids such as benzene, toluene, xylene, trichlorethylene, PCB and low boiling point organic vapors,
Materials such as natural rubber, synthetic natural rubber, styrene rubber, and butadiene rubber can be used. Leakage substances to be detected are water (including water containing radioactive substances), pure water, saline, hydrochloric acid,
For aqueous solutions such as sulfuric acid, nitric acid, aqueous ammonia, sodium hydroxide, etc. and water vapor, materials such as superabsorbent resin and cellulose can be used. Furthermore, by using a swelling material formed by kneading powdery particles of a super absorbent polymer with rubber, any of the above leaked substances can be detected at the same time.

The shielding member may be directly fixed to the swelling material, or a supporting mechanism may be separately provided and movably supported on the supporting mechanism. The light reflecting portion of the shielding member can be formed using a material having a light reflecting property such as aluminum. For example, the surface of a metal such as stainless steel or copper or an epoxy resin or a polymer such as rubber may be wet- or dry-plated with light-reflective aluminum or the like. The light reflecting portion may be provided on the surface of the shielding member on the incident light side. The thickness of the shielding member may be such that it can smoothly move in the internal space, and may be, for example, several mm or less.

It should be noted that the beam, which is adjacent to a light source such as an LED or LD connected to the end of the optical fiber on the incident light side of the optical fiber,
It is possible to detect various leaked substances by inserting a splitter and detecting the presence / absence of reflected light from the light reflecting portion by a signal processor having various photodiodes as light receiving elements.

Targeting such a leak detector, each invention of the present application uses the following configuration. According to the first aspect of the invention, the swelling material storage chamber has a structure that prevents the swelling material from moving before swelling and restrains the swelling material so that the swelling material swells toward the internal space. Further, the leaking substance introducing portion is provided on the wall portion of the housing facing the internal space with the swelling material interposed therebetween.

When coupling a pair of optical fibers through the internal space, the end faces of the optical fibers can be directly opposed to each other. However, since the coupling loss becomes large, a problem occurs when a large number of leak detectors are connected in series. Therefore, in the invention of claim 2, a microlens is arranged at each end of the pair of optical fibers to reduce the coupling loss. When arranging a microlens, for example, one end face of an optical fiber is connected to a microlens such as a rod lens, and the tip end face of this microlens is an engineering plastic such as an epoxy resin or a metal such as stainless steel or aluminum. Can be fixed so as to form a smooth surface in conformity with the side surface of the rigid support manufactured by a method such as molding or mechanical molding. When connecting the optical fiber to the microlens, the optical fiber may be fixed to the rigid support or may be detachably connected using a commercially available connector. When using a microlens, it is necessary to make the stroke of the shielding member larger than the diameter dimension of the microlens in order to reliably reflect the incident light to the optical fiber on the incident side when the swelling material swells. . For example, by setting the stroke of the shielding member to be 1 to 10 times the diameter of the microlens, precise positioning of the light reflection part is not necessary, and stable leakage that is not affected by vibration, temperature, weight, etc. A detector can be obtained.

According to the third aspect of the present invention, the swelling material is accommodated in the swelling material accommodating chamber while being pressed by the wall portion of the housing provided with the leakage substance introducing portion. The leaking substance introducing portion is composed of a porous portion formed entirely on a portion of the wall portion of the housing that comes into contact with the swelling material. Here, the porous portion may have any structure as long as it can introduce the leaked substance into the housing, and may be composed of, for example, a large number of through holes penetrating the wall portion in the thickness direction. A sponge structure or the like may be used. Specifically, wire mesh, various porous metals such as sintered metal, various porous plastics, various cloths, and the like can be used, and porous PTFE can also be used to make them water repellent. Further, in the case where foreign matter does not accumulate in this portion, only the frame for fixing the swelling material may be used.

According to the fourth aspect of the present invention, the internal space is formed in an airtight state, and then a pressure adjusting chamber whose volume is increased / decreased according to a change in external pressure or internal pressure is provided, and the pressure adjusting chamber and the internal space are communicated with each other. .

According to the fifth aspect of the present invention, the internal space and the swelling material storage chamber are continuously provided, and the swelling material does not have air permeability and has a seal layer on the internal space side that hermetically seals the internal space. In addition, the other part is porous. As such a swelling material, use one that has a composite structure in which the side that comes into contact with the leaked substance first is made of a material that is permeable porous or has many voids, and the inner space side is a thin, bubble-free sheet. You can Examples of the composite structure include a thin sheet with a large number of protrusions, a large number of holes formed on one side of a substrate so as not to penetrate small holes, and a thin porous material with fine particles welded or bonded. There are things such as a sheet bonded.

According to a sixth aspect of the present invention, like the leakage detectors of the first to fifth aspects, a pair of optical fibers arranged so that their optical axes coincide with each other for transmitting and receiving light, and swelling by absorbing a leaking substance. And the swelling material that moves to move between the pair of optical fibers by utilizing the swelling of the swelling material, and when the swelling material swells, locates the light reflection part in the optical path between the pair of optical fibers to make incident light incident on the incident side. A leak position can be easily detected when a plurality of leak detectors each including a shielding member that reflects toward an optical fiber are used. In the present invention, a plurality of leak detectors are arranged at a plurality of leak detection points, and a plurality of leak detectors are connected in series to form a leak detector row. Then, light is applied to the optical path of the leak detector array from one direction to measure the reflected light, and light is applied to the optical path of the leak detector array from the other direction to measure the reflected light and these two reflected lights are compared. Then, the leak position is detected.

[0025]

When the swelling material is constrained as in the first aspect of the invention, the swelling material does not move or vibrate even if vibration is applied from outside before swelling, and the swelling material expands in the inner space. Since it can be limited only to the heading direction, generation of an erroneous signal can be prevented. Further, when the leaked substance introducing portion is provided on the wall portion of the housing facing the internal space with the swelling material interposed therebetween, the swelling material can be swollen quickly in the direction toward the internal space, and the detection sensitivity of the detector is enhanced. be able to. Further, in the structure of the leak detector of the present invention, a plurality of leak detectors can be connected in series and used.

When a microlens is used as in the second aspect of the present invention, the coupling loss between the pair of optical fibers does not increase, so even if a plurality of leak detectors are connected in series, there is no problem in leaking. Can detect.

According to the third aspect of the present invention, if the leaking substance introducing portion is composed of the porous portion formed entirely on the portion of the wall portion of the housing that comes into contact with the swelling material, the leaking substance can be substantially removed from one surface side of the swelling material. It is possible to evenly absorb the swelling material, prevent local swelling of the swelling material from occurring, and more reliably move the shielding member in an appropriate direction.

When the inner space is made airtight (including liquidtight) as in the fourth aspect of the invention, for example, the hydrophobic organic liquid in the aqueous solution or the aqueous solution in the hydrophobic organic liquid can be detected. This is because the internal space is in an airtight state (including a liquid-tight state), so that a leaking substance or a solution does not enter the internal space to make measurement impossible or generate an erroneous signal. When the leak detector is placed in a solution and the internal space is made airtight, the external pressure changes depending on the position of the leak detector, causing deformation such that the swelling material bulges toward the inner space. Wake up. As a result, the shielding member may move to generate an erroneous signal. Further, when the pressure in the airtight internal space becomes high due to the rise in ambient temperature, the swelling material must swell against this pressure, which causes a problem that the shielding member cannot be moved sufficiently. There is a problem that this occurs or the detection sensitivity deteriorates. In the present invention, the pressure adjusting chamber whose volume is increased or decreased according to the change of the external pressure or the internal pressure is provided, and the pressure adjusting chamber is communicated with the internal space. Therefore, the swelling material is bulged toward the internal space by the external pressure. Such deformation does not occur, and even if the ambient temperature rises, the internal pressure of the internal space does not increase, and the occurrence of such a problem can be prevented.

As the swelling material according to the fifth aspect of the present invention, a swelling material that has no air permeability and has a seal layer that hermetically seals the internal space on the internal space side and the other portion is porous is used. With this, the movement of the shielding member due to the compression of the swelling material by the external pressure can be minimized to make the internal space airtight.
In addition, the porous portion enables absorption of an excessive increase in volume due to swelling, promotion of permeation of a leaked substance, and acceleration of swelling rate.

According to the sixth aspect of the present invention, the reflected light obtained by applying light from one direction to the optical path of the leak detector array in which a plurality of leak detectors are connected in series, and the leak detector array Comparing the reflected light obtained by giving light from the other direction to the optical path,
The leak position can be easily detected. The reflected light may be compared by comparing the light amount and the connection loss (dB). If one of the leak detectors detects the leak in advance and reflects the incident light by comparing the two reflected lights experimentally or theoretically, the measured two reflected lights By comparing the comparison result with the comparison data obtained in advance, the leak detector detecting the leak can be discriminated and the leak position can be detected. Also, in the case where two specific leak detectors among the plurality of leak detectors constituting the leak detector array detect the leak and are in the state of reflecting the incident light respectively, the comparison data is obtained in advance. In other words, the leakage range can be detected by comparing the comparison result of the two reflected lights with the comparison data obtained in advance. If there is no reflected light on one side,
It can be determined that the optical fiber in the route where the reflected light does not return has a break.

[0031]

【Example】

[Embodiment 1] An embodiment of the present invention will be described below in detail with reference to the drawings. 1A to 1C are longitudinal sectional views of the embodiment, a sectional view taken along line BB of FIG. 1A and C of FIG. 1A.
It is a -C line sectional view. In these figures, 1, 1'has a core diameter of 50 μm and a clad diameter of 125 μ.
Optical fiber 2, 2'consisting of m multimode optical fiber
And a pair of optical fiber cables 2 and 2'covering the optical fibers 2 and 2'and outer coatings 3 and 3'having a diameter of 2.8 mm. The outer coatings 3 and 3'at the ends of the optical fiber cables 1 and 1'are removed, and the portions of the optical fibers 2 and 2'exposed by the removal of the outer coatings 3 and 3'are made of a ceramic tube. Ferrules 4 and 4'are fitted via an adhesive. The exposed portions of the optical fibers 2 and 2'have their tips polished to reduce coupling loss. The ferrules 4 and 4'are fixed to the rigid support base 5, and the ferrules 4 and 4 '
The end surface of 4'is bonded to the rod lenses 6, 6'fixed to the rigid support 5. In addition, rod lenses 6, 6 '
A rod lens having a diameter of 1 mm and a quarter pitch length was used as

The rigid support base 5 is a half part 5 made of epoxy resin.
The a and the half portion 5b are joined by using an epoxy adhesive. Ferrules 4 and 4'on the rigid support 5.
Fitting holes 7 and 7'in which the rod lens 6 and 6'are fitted respectively, an internal space 8 and a recess 10a for forming a swelling material storage chamber 10 in which a swelling material 9 is stored are formed. Has been done. In practice, the rigid support 5 is inserted into the stainless steel holder 11, and the stainless steel sintered metal cover 12 is fitted to the holder 11.
The swelling material storage chamber 10 is configured.

The internal space 8 has a pair of optical fibers 2, 2 '.
Of the first space 8 extending in a direction (hereinafter, referred to as an orthogonal direction) orthogonal to the direction in which the optical axis of (hereinafter, referred to as the optical axis direction) extends.
a and a second space 8b located on the swelling material storage chamber 10 side and extending in the optical axis direction. The first space 8a is
The plate-shaped shielding member 13 fixed to the swelling material 9 is formed in a shape that allows smooth movement, and specifically, the gap between the exposed end faces of the rod lenses 6 and 6'is configured to be 1 mm. Has been done. And the 2nd space 8b is formed in the shape which guides the swelling material 9 so that the swelling material 9 may swell centering on the part to which the shielding member 13 is being fixed. The swelling material storage chamber 10 in which the swelling material 9 is stored is formed by being surrounded by the inner wall surface of the recess 10 a, the inner wall surface of the cover 12, and the inner wall surface of the holder 11, and the movement of the swelling material 9 before swelling And the swelling material 9 prevents the internal space 8
The swelling material is constrained so that it swells toward. When the cover 12 is attached, the swelling material 9 is pressed or compressed in the orthogonal direction and stored in the swelling material storage chamber 10.

In this embodiment, a breathable foam of polyisoprene rubber is used as the swelling material 9. This swelling material has a property of swelling when absorbing a hydrophobic organic liquid and a low boiling point organic substance vapor, and has air permeability in the thickness direction (orthogonal direction). Therefore, in this embodiment, the internal space 8
Communicate with the external space through the swelling material 9.

The holder 11 has a tubular shape with both ends in the optical axis direction being open and having a rectangular cross section. The holder 11 has a fitting portion 1 into which the cover 12 is fitted.
1a is formed. The rigid support 5 is fitted to the inside of the holder 11 through an adhesive agent at substantially the center thereof, and epoxy resin is provided in the openings 11b and 11b 'of the holder 11 where both ends of the rigid support 5 are located. Is filled with
Sealing portions 14 and 14 'are formed. In this embodiment,
The rigid support 5 and the sealing parts 14 and 14 'constitute a holding part for holding the optical fiber, and the holder 1
1, the cover 12, a part of the rigid support base 5, and the sealing portion 1
A housing is constituted by 4, 14 '. The cover 12 is located at a position facing the internal space 8 with the swelling material 9 in between, and constitutes a part of the wall portion of the housing. The cover 12 may have a porous portion forming a leaking substance introducing portion for introducing the leaking substance, at least at a portion in contact with the one end surface 9a positioned in the orthogonal direction of the swelling material 9.
The swelling speed of the swelling material 9 can be maximized by forming the leaking substance introducing portion in the entire portion of the cover 12 that contacts the end surface 9a of the swelling material 9. In the present embodiment, the cover 12 is fixed to the holder 11 with an adhesive, but the cover 12 is detachably attached to the holder 11.
The swelling material may be exchangeable depending on the leaked substance to be detected.

The shielding member 13 is provided on the other end surface 9b of the swelling material 9 which is located in the orthogonal direction so as to move in the orthogonal direction orthogonal to the optical axis with a minute gap between the end surfaces of the rod lenses 6 and 6 '. It is fixed using epoxy resin. Light-reflecting portions are formed on both surfaces of the shielding member 13 in the thickness direction. In this example, a light reflecting portion was formed by vapor-depositing aluminum on a rectangular stainless steel plate having a thickness of 0.8 mm. When the swelling material 9 is not swollen, the shielding member 13 is displaced under the influence of vibration, temperature, load, etc., so as not to block the optical path of the pair of optical fibers 2, 2 '. 13 has at least about 20 tips
The shielding member 13 is attached to the swelling material 9 so as to be separated by 0 μm. As a result, before the swelling material 9 swells, the incident light is surely passed as it is as the output light. When the swelling material 9 swells, the shielding member 13 shields the optical path so that the incident light is reflected and the output light does not go to the subsequent portion. It is 1.2 times or more the diameter of the rod lenses 6 and 6 '. This eliminates the need for precise positioning of the shield member 13 and provides a stable leak detection device that is not affected by vibration, temperature, weight, etc.

When various hydrophobic organic liquids such as gasoline, kerosene, heavy oil, lubricating oil, benzene, and trichloroethylene, or aqueous solutions or vapors containing them enter the swelling material storage chamber 10 through the cover 12, the swelling material 9 leaks out. Absorbs substances and swells. Since the swelling material storage chamber 10 restrains the swelling material 9 in a direction in which the swelling material 9 expands toward the internal space 8, the swelling material 9 expanded by the swelling expands into the second space 8b of the internal space 8. Put out. Since the second space 8b forming the guide portion guides the swelling material 9 so that the swelling material 9 swells around the portion where the shielding member 13 is fixed, the shielding member 13 is orthogonal to the second space 8b. Move smoothly in the direction.

In the above embodiment, the housing is composed of the holder 11, the cover 12, a part of the sealing portion 14 and a part of the rigid support base 5. However, the holder 11 is formed in a box shape and the housing is composed of only the holder. May be configured. Further, in the above embodiment, the cover 12 is provided with the leaking substance introducing portion. However, without using the cover 12, a large number of through holes are directly formed in the holder to provide the leaking substance introducing portion on the wall portion of the housing. You can also

[Embodiment 2] Next, another embodiment of the present invention will be described in detail with reference to FIG. 2A is a vertical cross-sectional view of the leak detector of the embodiment, and FIG. 2B is a cross-sectional view taken along the line BB of FIG. 2A. In FIG. 2, the same members as those shown in FIG. 1 are denoted by the same reference numerals as those in FIG. 1 plus 100. The present embodiment differs greatly from the embodiment of FIG. 1 in that the rigid support 105 is provided with a recess 105A at substantially the center of the end in the width direction.
The storage space 117 is formed between the storage space 117 and the wall portion 111b of the storage space 117, the bag body 115 that configures the pressure adjustment chamber is stored in the storage space 117, and the storage space 117 and the internal space 108. Communication passage 11 communicating with the first space 108a
6 is formed on the rigid support 105.

The storage space 117 communicates with the space outside the holder 111 through the porous portion of the cover 112.
The bag 115 that constitutes the pressure adjusting chamber has a structure formed in an accordion shape using an impermeable polyethylene film. The peripheral edge of the opening of the bag 115 is airtightly joined to the wall surface of the rigid support 105 through an appropriate fixing means such as an adhesive. In addition, the structure of the pressure adjusting chamber is such that the internal space 1 is breathed by external pressure or the volume is changed according to the change of internal pressure.
Any shape or structure may be used as long as the inner pressure and the outer pressure of 08 can be equalized and the deformation of the swelling material 109 can be suppressed.

The swelling material 109 includes a plurality of small holes 109c having a bottom from one surface 109a side in the polyisoprene rubber sheet.
It is formed by opening a large number of ... And the swelling material 10
9 is a surface 109b on the side where the small holes 109c are not formed.
Is housed in the swelling material housing chamber 110 with the side facing the inner space 108. The restraint relationship between the swelling material 109 and the swelling material storage chamber 110 is the same as the restraint relationship between the swelling material 9 and the swelling material storage chamber 10 of the first embodiment.
The surface 109b of the swelling material 109 is adhered to the bottom of the recess 110a of the rigid support 105 using an adhesive to keep the internal space 108 airtight. Also, the surface 1 of the swelling material 109
A blocking member 113 is fixed to 09b. The structure of the blocking member 113 is the same as that of the blocking member 13 of the first embodiment. In this embodiment, a part of the swelling material 109 has a non-air-permeable structure to make the internal space 108 in an airtight (including liquid-tight) state. However, in addition to the swelling material 109, it can be deformed from synthetic resin or rubber. A seal sheet is adhered to the bottom of the recess 110a to make the internal space 108 airtight, and then the first embodiment is placed thereon.
A swelling material having air permeability may be stored in the same manner as the swelling material 9 used in the above. In this case, the shielding member may be fixed to the back surface of the seal sheet. Further, in this embodiment, the small holes 109c are provided in the swelling material 109 in order to increase the swelling speed of the swelling material 109.
Of course, the entire swelling material 109 may be made a non-air-permeable porous material without providing c ...

In the leak detector of this embodiment, the internal space 10
Since 8 can be configured to be airtight (liquid-tight) and the internal pressure of the internal space can be adjusted, it is possible to detect a specific leaked substance in the liquid without any trouble.

[Embodiment 3] An example of the leak detection system for carrying out the method of the present invention will be described in detail below with reference to FIG. Here, X1 to Xn are as shown in FIG.
And the leak detector 21 and the optical connector 2 as shown in FIG.
This is a leak detection unit in which 2a and 22b are combined into one unit. In this system, these leak detection units X1 to Xn are connected in series to form a leak detector array 2
Make up three. Reference numeral 31 denotes a light source using a light emitting diode, and the beam splitter 3 is adjacent to the light source 31.
2 are arranged. The beam splitter 32 receives the reflected light, and the reflected light received by the beam splitter 32 is passed through a light receiver 33 that converts an optical signal into an electric signal by using the Si-APD as a light receiving element and a signal processor 35.
Entered in. The signal processor 35 includes a leak detector array 23.
The light that has passed through is converted into an electric signal by the light receiver 34 having the Si-APD as a light receiving element and is input. Further, in this system, an optical fiber switch 36 for switching the light source side and the receiving side is connected to both ends of the leak detector row 23.

The signal processor 35 is switched so that the optical fiber switch 36 guides the light from the light source 31 in the direction (forward direction) through which the leak detector unit 23 passes through the leak detector units X1, X2, ... Xn in this order. If so, an operation is performed to determine the occurrence of leakage and the occurrence of disconnection of the optical fiber. When at least one leak detector 21 detects a leak, the swelling materials 9, 109 swell and the shielding members 13, 11
3 blocks the optical path, the light from the light source 31 is reflected and returns to the light source 31 side. When this reflected light is received through the beam splitter 32, the signal processor 35 determines that leakage has occurred. While the signal processor 35 is receiving a signal indicating that light is being received from the light receiver 34,
Judge that no leak has occurred. In addition, the signal processor 35
When neither of the light receivers 33 and 34 receives a signal indicating that light is being received, it is determined that the optical fiber in the optical path is broken.

After detecting the occurrence of leakage, the signal processor 35 performs the operation of detecting the leakage position and determining whether or not the optical fiber is broken. First, light is applied from the light source 31 to the leakage detector array 23 in the forward direction and the reflected light is measured. After that, the optical fiber switch 36 is switched to the leakage detector array 23 in the reverse direction (leakage detection units Xn, Xn-1, ... X1).
Light is applied from the light source 31 in the order of (the direction in which light passes) and the reflected light is measured. Then, the leakage position is detected by comparing the data obtained by comparing these two reflected lights with the comparison data obtained in advance. In this embodiment, the connection loss (d) of the two reflected lights is
The leak position is detected based on the comparison data in B).
Further, in the present embodiment, the comparison data of the connection loss (dB) of the two reflected lights under various conditions, which is experimentally or theoretically obtained in advance, is stored in the internal memory of the signal processor 35, and is automatically stored. The leak position can be detected.

Using the leak detector of Example 1 in this system, a test was conducted in which a small amount of various hydrophobic organic liquids such as gasoline, kerosene, heavy oil, lubricating oil, benzene, and trichloroethylene were brought into contact with the system. It is confirmed that the signal from the light receiver 33 changes the presence or absence of incident light in the signal processor 35, and the signal from the light receiver 33 changes the signal from the signal processor 35.
It was confirmed that the reflected light changes from nothing to. In this system, the leak detector 21 and the optical connectors 22a, 2
The average connection loss of one leak detection unit X composed of 2b was about 2 dB. The optical fiber usually has a transmission loss of 1 dB or less per 1 km, which is smaller than the connection loss of the leak detection device 21 and the optical fibers 22a and 22b, and can be practically ignored. Therefore, by measuring the connection loss of the reflected light in both the forward direction and the reverse direction, it is possible to accurately identify the leak detection unit that detects the occurrence of the leak.

[0047]

According to the first aspect of the present invention, the swelling material does not move or vibrate even if vibration is applied from outside before swelling, and the swelling material expands only in the direction toward the internal space. Since it can be limited, there is an advantage that an erroneous signal can be prevented from occurring. Further, since the leaking substance introducing portion is provided on the wall portion of the housing facing the internal space with the swelling material interposed therebetween, the swelling material can be swollen quickly in the direction toward the internal space, and the detection sensitivity of the detector is enhanced. There is an advantage that can be. Further, in the structure of the leak detector of the present invention, a plurality of leak detectors can be connected in series and used.

According to the second aspect of the present invention, there is an advantage that even if a plurality of leak detectors are connected in series, the leak can be detected without trouble.

According to the third aspect of the present invention, the leaked substance can be absorbed almost uniformly from the one surface side of the swelling material, and the swelling of the swelling material can be prevented from being locally biased, and the shielding member can be prevented. Has the advantage that it can be moved more reliably in the appropriate direction.

According to the invention of claim 4, there is an advantage that the hydrophobic organic liquid in the aqueous solution and the aqueous solution in the hydrophobic organic liquid can be detected. Moreover, even if the internal space is made airtight,
Since a pressure adjusting chamber whose volume increases or decreases according to changes in external pressure or internal pressure is provided and this pressure adjusting chamber is communicated with the internal space, deformation such that the swelling material bulges toward the internal space due to external pressure is prevented. It does not occur, and even if the ambient temperature rises, the internal pressure of the internal space does not increase, and there is an advantage that an erroneous signal can be prevented.

According to the fifth aspect of the present invention, there is an advantage that the movement of the shielding member due to the compression of the swelling material by the external pressure can be minimized to make the internal space airtight. Further, it is possible to absorb an excessive increase in volume due to swelling, promote permeation of a leaked substance, and accelerate the swelling speed.

According to the invention of claim 6, there is an advantage that the leak position and the range can be easily detected when a plurality of leak detectors are connected in series.

[Brief description of drawings]

1A is a vertical cross-sectional view of an embodiment of the present invention, FIG. 1B is a cross-sectional view taken along line BB of FIG. 1A, and FIG. 1C is C of FIG. 1A.
It is a -C line sectional view.

2A is a vertical cross-sectional view of a leak detector according to another embodiment of the present invention, and FIG. 2B is a cross-sectional view taken along line BB of FIG. 2A.

FIG. 3 is a block diagram showing the configuration of an example of a leak detection system for implementing the method of the present invention.

[Explanation of symbols]

 1, 1 ', 101, 101' Optical fiber cable 2, 2 ', 102, 102' Optical fiber 3, 3 ', 103', 103 Outer coating 4, 4'Ferrule 5, 105 Rigid support stand 6, 6 ', 106, 106 'Ferrule 7, 7', 107, 107 'Fitting hole 8, 108 Internal space 9, 109 Swelling material 10, 110 Swelling material storage space 11, 111 Holder 12, 112 Cover 13, 113 Shielding member 14, 114 Sealing part 115 Bag (pressure adjusting chamber) 116 Communication path 21 Leakage detector 22a, 22b Optical connector 23 Leakage detector row 31 Light source 32 Beam splitter 33, 34 Light receiver 35 Signal processor 35

Claims (6)

[Claims] 1. A pair of optical fibers, the ends of which are respectively held by a holding portion provided inside the housing so as to match the optical axis with the housing and which transmits and receives light through an internal space of the housing. A leaking substance introducing portion provided on a wall portion of the housing, and a swelling material which is disposed in a swelling material accommodating chamber provided in the housing and absorbs and leaks a leaking substance to be detected which has entered from the leaking substance introducing portion. And moving in the internal space by utilizing the swelling of the swelling material,
When the swelling material swells, a light reflecting portion is located in the optical path between the pair of optical fibers, and a shielding member that reflects the light incident on the internal space toward the optical fiber on the incident side is provided. The swelling material accommodating chamber has a structure that prevents movement of the swelling material before swelling and restrains the swelling material so that the swelling material swells toward the inner space. The leak detector is characterized in that the portion is provided on a wall portion of the housing facing the internal space with the swelling material interposed therebetween. 2. The leak detector according to claim 1, wherein a microlens is arranged at each of the ends of the pair of optical fibers. 3. The swelling material is stored in the swelling material storage chamber in a state of being pressed by the wall portion of the housing where the leaking substance introducing portion is provided, and the leaking substance introducing portion is the wall portion. The leak detector according to claim 1, wherein the leak detector is formed of a porous portion formed entirely in a portion that comes into contact with the swelling material. 4. The internal space is formed in an airtight state, and a pressure adjusting chamber whose volume increases or decreases according to changes in external pressure or internal pressure is further provided, and the pressure adjusting chamber and the internal space communicate with each other. The leak detector according to claim 1, wherein: 5. The inner space and the swelling material storage chamber are continuously provided, and the swelling material does not have air permeability, and a sealing layer for hermetically sealing the inner space is provided on the inner space side. The leak detector according to claim 4, wherein the leak detector is provided in the first part, and the other part is porous. 6. A pair of optical fibers arranged so that their optical axes coincide with each other for transmitting and receiving light, a swelling material that absorbs a leaked substance and swells, and a pair of the optical fibers that utilize the swelling of the swelling material. A shielding member that positions the light reflecting portion in the optical path between the pair of optical fibers when the swelling material moves between fibers and swells, and reflects incident light toward the optical fiber on the incident side. A plurality of leak detectors are arranged at a plurality of leak detection points, and a plurality of leak detectors are connected in series to form a leak detector row. An optical path of the leak detector row is arranged from one direction. The reflected light is measured by applying light, the reflected light is measured by applying light from the other direction to the optical path of the leak detector array, and the leak position is detected by comparing the two reflected lights. Leakage position detection method.